extrapolated to natural zooplankton abundance, should indicate levels of DOC production by 

 these grazers in the absence of bacterial uptake. Because small changes (<5 |iM C) in DOC 

 cannot accurately be measured in the face of large background concentrations of naturally- 

 occurring DOC, total dissolved carbohydrate concentration (via an improved MBTH assay) 

 will be measured as a proxy for DOC. Total dissolved carbohydrates have recently been 

 shown to comprise a sizeable fraction of total DOC in oligotrophic waters and, as 

 carbohydrates are a significant biochemical component of bacteria, phytoplankton, and 

 zooplankton, these compounds are expected to be a major by-product of grazing. 



H. Production and Transformations of Detrital POC 



An in situ collector will be used to obtain sinking aggregates and pellets. The instrument 

 will consist of a gentle suction collector operated by a pump, and the collections can be made 

 to depths of several 100 m. Using this visually guided system, relatively undisturbed, larger 

 particles (>1 mm) will be collected from the water column for shipboard rate measurements of 

 associated processes. Transformations of carbon and various nutrient elements (N, Si, P) from 

 particles into dissolved organic and inorganic pools will be measured in conjunction with other 

 components in the project. The incubated particles and their associated communities will be 

 contrasted with particles collected by traps, to assure these incubated particles represent 

 "typical" sinking material in the study area. 



The vertical export of particulate organic carbon from the euphotic zone will be measured 

 at three selected sites in the Cape Hatteras region. These stations will be the same as the 

 inner shelf, middle shelf and shelf /slope boundary process stations described herein. 

 Measurements of export will be accomplished using free-floating MULTTTRAP design 

 sediment traps placed below the photic zone and at another selected depth beneath the photic 

 zone. Each deployment will be for 48 hours in duration and will include both formalin 

 preserved traps and screened (333 |im mesh) unpreserved traps so that we may address the 

 degree to which POC is exported to the shelf sediments. Traps will also be included to look 

 for the vertical export of phytoplankton pigments and nuclides, especially Pu) we can estimate 

 maximal bomb ^'^C in bulk samples of finite age (5^'^C < 0). 



38 



